A factory has two machines that produce bolts. Machine I produces 80% of the daily output of bolts, and 9% of its bolts are defective. Machine II produces 20% of the daily output, and 5% of its bolts are defective.

So what is the question?

0.2 To determine the overall percentage of defective bolts produced by the factory, we need to calculate a weighted average of the defect rates of the two machines.

Step 1: Calculate the weighted proportion of bolts produced by each machine.
- Machine I produces 80% of the daily output, so its weighted proportion is 0.8.
- Machine II produces 20% of the daily output, so its weighted proportion is 0.2.

Step 2: Calculate the weighted defect rate for each machine.
- Machine I has a defect rate of 9%, so its weighted defect rate is 0.09 * 0.8 = 0.072 (7.2%).
- Machine II has a defect rate of 5%, so its weighted defect rate is 0.05 * 0.2 = 0.01 (1%).

Step 3: Calculate the overall weighted defect rate.
- The overall defect rate is the sum of the weighted defect rates, which is 0.072 + 0.01 = 0.082 (8.2%).

Therefore, the factory has an overall defect rate of 8.2%.